macro_rules! calculate {
    (eval $e:expr) => {{
            {
                let val:usize = $e;
                println!("{} = {}",stringify!{$e},val);
            }
        }};
}

fn main() {
    println!("Hello, world!");
    calculate! {
    eval 1 + 2
    }

    calculate! {
        eval (1+2)*(3/4)
    }
}
